Method of reducing viscosity of drilling fluids during drilling



Dec. 24, 1963 J. w. GRAHAM ETAL 3,115,195

METHOD OF REDUCING VISCOSITY OF DRILLING FLUIDS DURING DRILLING Filed Aug. 28, 1961 FIG. I-

STAND PIPE FUEL INJECTOR FLUID RETURN ATTORNEY.

IQAQ' V- 9S A kcuwmss if l6 1 E GUARD I6 4; SLEEVE g PLATINUM DRILL PIPE4 IGN'TER T\ F sue 1 5 l3 |5- l-JGNITER l4 COMBUSTION i I ZONE I 8- MAXIMUM TEMP. 1 2,

S ,7 AREA O f g INVENTORS. JOHN K- KERVER, 11 an B Jomy. s A HAM, 2px 'Z United States Patent Delaware Filed Aug. 28, 1961, Ser. No. 134,216 2 Claims. (Cl. 175-17) The present invention concerns a technique for increasing well drilling rates when using water as the drilling fluid.

It is known that in drilling wells the drilling rate increases with decreases in viscosity of the drilling fluid. It is also known that the viscosity of water is lowered by heating. Therefore, when drilling with water, increased drilling rates are obtainable by heating the circulating drilling water. The reduction in viscosity of the water must be in the vicinity of the drill bit; however, when the water is heated at the surface of the earth, it is difficult and expensive to supply water at the drill bit sufiiciently hot to reduce the viscosity enough to cause an increase in the drilling rate. Drilling water heated at the earths surface loses excessive heat to the surroundings, and, in particular, much heat is lost by conduction through the drill pipe to the drilling fluid returns flowing through the annulus between the drill pipe and the borehole wall.

A primary object of the present invention is to overcome disadvantages encountered in heating drilling water at the surface of the earth to increase drilling rates by providing a novel, improved method for heating the circulating water doWn-the-hole in order to supply sufficient heat to decrease the viscosity of the water adjacent the drill bit.

Briefly, the invention comprises the steps of intermittently injecting slugs of a combustible fuel, e.g., natural gas, methane, diesel oil, kerosene and an oxidizer fuel, e.g., air or oxygen, into the circulating drilling water at the earths surface and then reacting the mixture in the drill pipe preferably close to the drill bit to heat the water and reduce the viscosity thereof.

The above object and other objects of the invention will be apparent from a more detailed description of the invention taken in conjunction with the drawings in which:

FIG. 1 is a diagrammatic illustration of the method of the invention; and

FIG. 2 is an enlarged cross-sectional view of that portion of the drill pipe which forms the combustion zone.

Referring to the drawings in greater detail, the lower portion of FIG. 1 shows a borehole in which is arranged a drill bit 11 and attached drill pipe 12. As seen more clearly in FIG. 2, dr-ill pipe 12 is provided near bit 11 with a sub 13 containing a platinum catalyst igniter 14 and a guard sleeve 15 to shield igniter 14.

3,115,195 Patented Dec. 24, 1963 ice The globules 16 represent cuttings being carried upwardly by the circulating water.

The upper portion of FIG. 1 shows the surface equipment. A surface casing 17 is shown cemented in borehole 10 and provided with conventional surface control equipment 18. A water return line 19 connects to casing 17 to carry the return water and cuttings from the annulus between casing 17 and drill pipe 12. A derrick floor 28 and rotary 21 are shown, as well as a water pump 22, which feeds water from a water source 23 to drill pipe 12 through a conduit 24. A fuel injector or pump '25 injects a combustible fuel and oxidizer mixture into water line 24 through a conduit 26 from fuel and oxidizer sources 27 and 28, respectively.

The operation is as follows. During drilling, water is pumped from water source 23 by pump 22 through conduit .24 into the interior of drill pipe 12 and is circulated down therethrough and up annulus A between drill pipe 12 and the wall of borehole 184 to water return line 19, which discharges the drilling water and retained cuttings into a suitable reservoir 38. Intermittently, slugs of a combustible fuel and oxidizer, e.g., methane and air, are injected by means of fuel injector 25 from fuel and oxidizer sources 27 and 28, respectively, into water line 24. The combustible mixture slugs are carried down drill pipe 12, and adjacent sub 13 are ignited by platinum igniter 14. Ignition is spontaneous upon contact of the combustible mixture with the igniter, and no surface connections are needed. Guard sleeve 15 is used to protect the igniter insert 14 from the circulating water.

The heat generated in the combustion zone 31 heats the circulating water to a maximum temperature at the bottom of the hole where it is needed. The sensible heat contained in the water returning up annulus A is used in part to heat the water circulating down drill pipe 12.

Having fully described the method, elements, and objects of the invention, we claim:

1. A method for increasing well drilling rates when drilling with water where water is circulated from the earths surface through the drill bit and back to the earths surface during drilling comprising the steps of: injecting intermittently into the circulating drilling water at the earths surface slugs of a combustible mixture; and igniting the combustible mixture slugs in the vicinity of the drill bit and before the circulating water passes through the drill bit to thereby heat the circulating water and reduce its viscosity adjacent the drill bit.

2. A method as recited in claim 1 in which the combustible mixture slugs comprise natural gas and air.

References Cited in the file of this patent UNITED STATES PATENTS 2,073,448 Furth et a1. Mar. 9, 1937 2,887,160 Priester et a1. May 19, 1959 2,896,914 Ryan July 28, 1959 

1. A METHOD FOR INCREASING WELL DRILLING RATES WHEN DRILLING WITH WATER WHERE WATER IS CIRCULATED FROM THE EARTH''S SURFACE THROUGH THE DRILL BIT AND BACK TO THE EARTH''S SURFACE DURING DRILLING COMPRISING THE STEPS OF: INJECTING INTERMITTENTLY INTO THE CIRCULATING DRILLING WATER AT THE EARTH''S SURFACE SLUGS OF A COMBUSTIBLE MIXTURE; AND IGNITING THE COMBUSTIBLE MIXTURE SLUGS IN THE VICINITY OF THE DRILL BIT AND BEFORE THE CIRCULATING WATER PASSES THROUGH THE DRILL BIT TO THEREBY HEAT THE CIRCULATING WATER AND REDUCE ITS VISCOSITY ADJACENT THE DRILL BIT. 